Mercury May Be Hiding Water Ice, NASA Spacecraft Reveals

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New evidence from the first probe to orbit Mercury is building
support for the idea that the tiny planet may be harboring water
ice in some of its most extreme terrain.

Certain areas of Mercury's poles were previously found to be
bright in radio waves detected by radar measurements from the
Arecibo Observatory in Puerto Rico. Now, the
Messenger spacecraft has found that those same bright radar
spots appear to be in permanent shadow, according to camera views
from the probe's Mercury Dual Imaging System (MDIS).

"We've never had the imagery available before to see the surface
where these radar-bright features are located," Nancy Chabot, an
instrument scientist for MDIS at the Johns Hopkins University
Applied Physics Laboratory, said in a statement. "MDIS images
show that all the radar-bright features near Mercury's south pole
are located in areas of permanent shadow, and near Mercury's
north pole such deposits are also seen only in shadowed regions,
results consistent with the water-ice hypothesis."

The
Messenger probe's Mercury findings are not conclusive,
though. Those bright spots could represent some other substance,
the researchers said. Plus, some pieces of evidence don't fit
together perfectly.

For example, some of the craters are thought to have temperatures
inhospitable to water ice. Many of the locations would require a
thin layer of insulation to keep the ice colder than the surface,
which is thought to be slightly too warm, Chabot said.

Ultimately, the scientists have a better picture of these
intriguing areas now than ever before, and they hope to solve the
mystery with further study in the future.

If there is water ice on Mercury, the planet will not be alone.
Earth's moon, which is only slightly smaller than Mercury, also
seems to have water ice at its poles. Evidence for frozen water
has also been found on Mars and many asteroids in the solar
system.

Messenger (short for MErcury Surface, Space ENvironment,
GEochemistry and Ranging) launched toward Mercury 2004, and
arrived in orbit in March 2011.The $446 million probe has
completed its initial one-year mission and is on an
extended mission at Mercury until March 2013.

Chabot presented her latest findings last week at the 43rd Lunar
and Planetary Science Conference in The Woodlands, Texas.

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